1. Field of the Invention
The invention relates to a device for demonstrating and testing the cosmetic qualities of an ophthalmic lens.
2. Description of Related Art
The cosmetic qualities of a lens relate in particular to its resistance to abrasion, to the absence of scratches as a result of specific treatment, and to the absence of coloring in the material of the lens and/or its anti-reflection treatment.
It is known to evaluate the cosmetic level of a lens by looking at neon tube through the lens. However that method requires a trained eye to obtain a result that is reliable.
Furthermore, patent document U.S. Pat. No. 1,336,010 describes a device for testing an ophthalmic lens, which device comprises both a bearing wall for bearing against a fixed surface and provided on its face opposite from its bearing face with a viewing target, and also a wall for supporting the lens, which wall is placed at a distance of about 40 millimeters (mm) from the face of said bearing wall that is provided with the target.
That known device is not suitable for demonstrating and testing the cosmetic qualities of an ophthalmic lens.
That type of V-section device has a support wall that is inclined at an angle of 45° relative to the bearing wall and thus to the viewing target. As a result there is a large field of observation and the distance between the lens and the target is large and not constant. As a result the observer systematically concentrates little on evaluating the qualities of the lens.
Furthermore, such an arrangement gives rise to a shadow of the support wall that impedes observation. The non-uniformity of contrast of the shadow is also troublesome, it is projected onto the target, and the observer tends to look in that direction as a result.
Finally, when the observer looks at the target through the lens, such a device gives rise to a perspective effect that deforms the vision of the patterns of the target.